This invention relates to joints between two metallic structural members and, more particularly but not exclusively, is concerned with a method of forming a joint between a first metallic structural member, which comprises a metallic member having a coating of heat-degradable material adhering thereto, and a second metallic structural member, which may be similar to the first structural member or may simply comprise a metallic member without a coating of heat-degradable material, and which can be welded to the metallic member of the first metallic structural member. The invention is concerned inter alia with a method of joining together two metallic pipe sections, at least one and generally both of the pipe sections including a lining of a heat-degradable material such as a glass, a plastics material, or a natural or synthetic rubber, for example nylon, polyethylene, polypropylene and polyurethane.
Hitherto, attempts to join together abutting ends of two metallic pipe sections, one or both of which sections are lined with a heat-degradable material, e.g. a plastics material, by welding together the abutting ends of the metallic pipe sections have frequently resulted in destruction of the heat-degradable material by the high welding temperatures normally involved or at least a discontinuity or imperfection in the heat-degradable material at the joint.